Intro Regulation of K+,Pi,Mg2+, Ca2+ Flashcards
1
Q
- Normal ranges for plasma K+
A
3.5-5.0 mEq/L
2
Q
- K+ distribution in the body
A
-
98% Intracellular
- 80% muscle cells (~150 mEq/L)
- 20% Other cells
- 2% Extracellular (3.5-5.0 mEq/L)
3
Q
- What accounts for the 30 fold difference between intracellular K+ and extracellular K+ concentrations?
A
- Na+-K+ ATPase
- NaK2CL (NKCC)
- K+ channe;s
- Transcellular distribution regulated by other factors (ie: hormones)
4
Q
- Define Hypokalemia
- What causes it?
A
- K+ < ~3.7 mE/L
- Caused by:
- Vomiting/diarrhea
- Insulin excess
- Deficiency
- Alkalosis
5
Q
- Define Hyperkalemia
- What can cause it?
A
- [K+] > 5.2 mEq/L
- Lethal if > 10 mEq/L
- Causes
- Excessive intake
- Tissue release (burns, hemolysis, rhabdomyolysis)
- Shifts from ICF to ECF (acidosis, insulin deficiency, tissue damage, hyperglycemia)
6
Q
- Define Pseudohyperkalemia
- What causes it?
A
- Artificially high [K+]
- Lysis of RBCs during blood draw
7
Q
- Major routes of K+ loss from the body
A
- Feces
- Urine
8
Q
- What is the effect of hyperkalemia on cardiac muscle cells?
- What is the effect of hyperkalemia on other cells?
A
- Hyperpolarizes membrane (bradycardia, ELEVATED T wave, less likely to fire AP)
- Hypopolarizes cell (makes it easier to reach threshold and fire AP)
9
Q
- What is the effect of hypokalemia on cardiac cells?
- What is the effect of hypokalemia on other cells?
A
- Hypopolarizes cell (tachycarida, low T wave)
- Hyperpolarization
10
Q
- How much Ca2+ do we need per/day?
A
1000 mg
11
Q
- How is the body calcium pool supplied?
A
- GI reabsorption via calcitriol
- Bone resorption via PTH and Calcitriol
*
12
Q
- How is Ca2+ from the body Ca2+ pool removed?
A
- Secretion into the GI tract
- Excretion via the kidneys
- Deposition in bone via calcitonin
13
Q
Hypocalcemia _ neuromuscular excitability
A
- Increases neuromuscular excitability
- Why you can see hypocalcemic tetany/spasticity
14
Q
- Hypercalcemia _ neuromuscular excitability
A
- Decreases
- Threshold shifts away from RMP (hyperpolarizes)
15
Q
- Regulators of Ca2+
A
PTH, Calcitonin, Calcitriol
16
Q
- What can cause elevated serum Ca2+?
A
- Primary hyperparathyroidism (lots of PTH secreted)
- Malignancy
17
Q
- What can cause low serum Ca2+?
A
- Hypoparathyroidism
- Renal Disease
- Vitamin D Deficiency
18
Q
- What is the required dietary intake of phosphorus?
A
- ~1500 mg/day
19
Q
- Where are the body pools for phosphorus located?
A
- 85%-BONE
- 14% cells
- 1% serum
20
Q
- How are body pools of phosphorus lost?
A
- Bone deposition
- Stool
- Urine
21
Q
- What are the four main regulators of phosphate metabolism?
A
- Dietary- phosphate intake and absorption
- Calcitriol- increases resorption from bone and absorption from intestine (increases body pool of phosphorus)
- PTH- resorption from bone directly, intestinal absorption thru stimulation of calcitriol production
- Renal tubular- reabsorption of phosphorus (Stimulated by tubular filtered load of phosphorus and inhibited by PTH)
22
Q
- Where is calcitriol produced?
A
- Kidneys
23
Q
- Where is Mg2+ stored in the body?
A
- 50% in bone
- 49% ICF (Especially muscle)
- 1 % ECF
24
Q
- What important cellular functions does Mg2+ play a role in?
A
- Nucleotide binding
- Enzymatic cofactor
- Glycolysis
- Proliferation
25
Q
- Mg2+ depletion is associated with what conditions?
A
- Migraine
- Depression
- Epilepsy
- SIDS
- Arrythmia
- Preeclampsia
- Muscle Cramps
26
Q
- What is normal TOTAL serum Mg2+?
- What is a normal FREE serum Mg2+?
A
- 8-2.2 mEq/L
- 8-1.0 mEq/L
27
Q
- Total Mg2+ consists of
- What is the most abundant
A
- Ionized Mg2+
- Diffusible Mg2+ complexes
- Nondiffusible (protein-bound) Mg2+
- Ionized Mg2+
